Comparison of nonlinear optical chromophores containing different conjugated electron-bridges: the relationship between molecular structure-properties and macroscopic electro-optic activities of materials

Abstract

In electro-optic (EO) materials, realization of large EO coefficients for organic EO materials requires the simultaneous optimization of chromophore first hyperpolarizability, acentric order, molecular shape etc. As these parameters are complicatedly inter-related, thorough analyses are required to understand the dependence of macroscopic EO activity upon chromophore structure and property. Herein, we presented the synthesis of three chromophores containing different conjugated electron-bridges by acidic and alkaline formylation. Electron-rich moieties thiophene and formyl-thiophene in the different positions of chromophores played the different roles of electron-bridge, site-isolator and electron-isolator, generating intriguing property variations of electron distribution of push–pull structure, intramolecular charge-transfer, solvatochromism, microscopic hyperpolarizability and related density functional theory calculation results. In addition these molecular structure–property relationships were rationally related to the EO activities to understand the impact of microscopic molecular property on macroscopic EO activities of materials.